Studies indicate that the primary area of danger for an emergency vehicle moving along a roadway is an intersection with another roadway. In order to address this danger, warning devices have been developed intended to alert vehicles moving along the intersecting roadway of the emergency vehicle as it approaches and enters the intersection. Typically, these warning devices include a light whose intensity light varies in a manner that draws attention to the light and the associated emergency vehicle even though the environment of the vehicle and the warning device is filled with other stimuli that compete for the attentions of nearby observers.
Several different approaches are well known for realizing the variable intensity required of such warning lights. For example, it is well known to use flashing lights such as strobe lights for warning devices. It is also known to use rotating or oscillating light beams that appear to an observer as the beams sweep past the observer.
Although rotating light beams are characterized by the type of high intensity useful at intersections, much of the light energy is directed away from the intersection inasmuch that the light beam rotates a full 360.degree.. Conventional stationary warning lights are unable to direct high energy flashes over a sufficiently large area required at an intersection. Oscillating light beams, however, are capable of directing a relatively constant, high energy signal over an area determined by the sweep angle of the beam. In conventional devices of this type, the sweep angle is limited and typically is less than to approximately 120.degree.. An example of such an oscillating light can be found in U.S. patent application Ser. No. 07/592,670, to Stanuch et al., filed Oct. 4, 1990. Although larger effective sweep angles can be created if two or more oscillating lights are ganged together, a larger sweep angle for a single oscillating beam is desirable.